Fluid treating method and apparatus



Nov. 23, 1965 A. HERSHLER FLUID TREATING METHOD AND APPARATUS Filed Aug.22, 1961 INVENTOR 45s flE/PSHA. El?

BY 4, W

ATTO R N EY United States Patent 3,219,318 FLUID TREATING METHGD ANDAPPARATUS Abe Hershler, 74 Tobin Ave., Great Neck, Queens, N.Y. FiledAug. 22, 1961, Ser. No. 133,215 24 Claims. (Cl. 259-1) The presentinvention relates to methods and apparatus for the treatment of fluidsand it relates more particularly to a novel method and apparatus for thestirring and agitation of liquids, powders and other fluid materials.

The stirring or agitation of liquids or powders in a container has longbeen conventionally eflected by mechanical means, such as immersedstirring paddles of the rotary or oscillating types, immersed stationarypaddles with the container rotating or oscillating, and both theimmersed paddles and the container rotating and oscillating relative toeach other. Stirring has been effected, particularly where it is desiredto maintain the contained fluid completely sealed thereby necessitatingthe obviation of mechanical linkage, by oscillating the containerrelative to its contents, the inertial force of the contents effectingthe agitation thereof. A magnetic linkage between a stirring element anda drive has also been resorted to. In the latter case, the stirringelement, a permanent magnet commonly in the shape of a rod, is locatedin the container and is magnetically coupled to an external magnetrotated by an electric motor to correspondingly rotate the stirrermagnet.

The conventional fluid stirring and agitation procedures, as typified bythose described above, possess many drawbacks and disadvantages. Thestirring action is of a gross periodic nature since the motive force ordrive is periodic and is transmitted to the fluid in an over-all manner.While turbulence and non-streamline flow may occasionally occur, this isvery limited both in duration and space and thus contributes little tothe over-all agitation. The general character of the fluid movement isnonturbulent and streamlined, as exemplified by a single vortex orrotary flow, which is highly inefficient for dispersing or dissolvingpurposes. While the agitation of large batches of liquids may beadequately accomplished by the conventional procedures, the stirring ofvery small masses of liquids or powders in small volume containers, astypified by rnicrostirring, is not practical with the conventionalstirrers by reason of the large minimum dimensions of these stirrers,and the drive linkages which necessitates the use of oscillator orshaker type of mechanisms with their consequent drawbacks.

It is thus a principal object of the present invention to provide anovel method and apparatus for the treatment of fluids.

Another object of the present invention is to provide a novel method andapparatus for the stirring and agitation of fluids such as liquids,powders and other fluid materials.

Still another object of the present invention is to provide a novelmethod and apparatus for stirring and agitating a fluid substantiallyuniformly throughout the volume thereof.

A further object of the present invention is to provide a novel methodand apparatus for uniformly stirring and agitating a fluid in acontainer independently of the configuration of the container.

Still a further object of the present invention is to pro- 3,219,318Patented Nov. 23, 1965 "Ice vide a novel method and apparatus forstirring and agitating minute quantities of fluid materials.

Still another object of the present invention is to provide a novelmethod and apparatus of the above nature characterized by itsversatility, flexibility, high efliciency, simplicity, low cost, andapplicability of the fluids of various physical properties.

Another object of the present invention is to provide a novel method andapparatus for stirring and agitating preselected regions of a fluid.

The above and further objects of the present invention will becomeapparent from a reading of the following description taken inconjunction with the accompanying drawings which illustrate preferredforms of the present apparatus wherein:

FIGURE 1 is a vertical sectional view of a preferred embodiment of thepresent invention;

FIGURE 2 is a vertical sectional view of another embodiment of thepresent invention;

FIGURE 3 is a vertical sectional view of still another embodiment of thepresent invention;

FIGURE 4 is a vertical sectional view of a further embodiment of thepresent invention;

FIGURE 5 is a vertical sectional view of still a further embodiment ofthe present invention; and

FIGURE 6 is a vertical sectional view of another embodiment of thepresent invention.

It has been discovered that a stirring or agitation of a fluidthroughout the volume thereof may be efliciently eflected by subjectinga plurality of permanent magnets dispersed or distributed in the fluidto a magnetic field rapidly varying in direction. Each of the magnetsexposed to the direction varying magnetic field has a motion impartedthereto which effects the agitation and stirring of the fluid in theambient region. Thus agitation is independently and directly imparted tothe spatially distributed regions in the fluid volume as contrasted tothe conventional stirring procedures where motion is transmitted to thefluid from the stirrer element or mechanism by way of the fluid itself.In the present process a thorough agitation is effected uniformlythroughout the fluid volume, and there is a relatively high relativemovement of adjacent fluids, a mechanism highly desired in stirringoperations, as distinguished from the conventional practice where suchrelative movement is radically less. The apparatus required to effectthe present stirring action is of the utmost simplicity, a plurality ofsmall permanent magnet elements capable of being dispersed or suspendedthroughout the fluid volume being treated and a solenoid, with orWithout a core of magnetic material, connected to a source ofalternating current.

The features and advantages of the subject stirring and agitating methodare numerous. The process may be effectively applied to fluids incontainers varying in size and configuration practically without limit,from millimeter bore tubes to large vats and tanks of any shapewhatsoever, as well as in containers defined by biologic organs orducts. Furthermore, the stirring action may be directed to preselectedregions of a given volume by simply focussing and locating the directionvarying magnetic field by the use of magnetic shims, directors, coresand by the shape and location of the solenoids. For example, a singledefined layer or a plurality of separate layers, or a concentratedregion in a fluid volume may be selectively stirred. Moreover, theintensity of agitation throughout the fluid volume or the selectedregions may be simply controlled by adjusting the parameters of themagnetic field, such as its intensity, frequency and waveform. By reasonof the absence of any mechanical coupling between the stirring elementdefining permanent magnets and the means for producing the alternatingmagnetic field, the stirring procedure may be effected in completelyclosed and sealed vessels which may be under high vacuum or highpressure conditioning, under varying temperature conditions, and understerile environments. In addition, highly combustible and explosivefluids may be safely treated since there is no sparking or ignition orimpact hazard, per se. The present method is highly versatile andapplicable to fluids of a wide range or physical properties such asliquids of various viscosities as exemplified by alcohol and glycerine.The subject apparatus and method is particularly suitable for stirringand agitating minute quantities of fluids where conventional meanspossess many drawbacks. Examples of such applications is in theagitation of radioactive solutions, biological and medicinal solutionsand in microchemical procedures generally. It should also be noted thatthe present stirring procedure may be readily applied to continuouslyflowing fluids, through conduits, pipes, or the like.

The stirring and agitation intensity and elficiency of the presentprocess is a function of many parameter-s. Included among these are thenumber of permanent magnet elements present per unit volume of the fluidbeing processed, the size and configuration of the magnet elements aswell as their coercive force, the frequency, wave shape, intensity andconfiguration of the motivating alternating field, and the viscosity anddensity of the fluid being stirred. The optimum ranges and values of theabove parameters are readily ascertainable.

Generally, the greater the desired stirring intensity per unit volume,the greater the number of particles and the higher the magnetic fieldstrength. Where the same mass of magnetic elements are employed, ashereinafter limited, the smaller the element the greater the stirring.The minimum size of the permanent magnet elements is that of the singlemagnetic domains, which vary in size with the permanent magneticmaterial between 0.01 and several microns in diameter. The maximumelement size depends on the viscosity of the fluid being treated and thestrength of the magnetic material. The maximum dimensions of thepermanent magnet elements is advantageously between 0.1 micron and 1centimeter. The shape of the magnet elements should be non-spherical andadvantageously of irregular and non-uniform configuration and preferablyin the shape of elongated needles or rods.

The magnet element shape may also be predetermined in which case theyare machined, cast, pressed or otherwise formed to the desiredconfiguration which is dictated by the type of magnet element motionsought as well as the type and efliciency of agitation and the materialforming the permanent magnet element. Examples of such predeterminedshapes are I, X, H, L or the like. Moreover, the permanent magnetelements may be coated or otherwise encased in a preferably thin layerof a material inert to the fluid being treated such as a polyolefin, ahalogenated polyolefin, for example, polytetrafluoroethylene, glass,rubber, a silicone or the like.

The coercive force of the magnet elements should be as large as possibleand should advantageously exceed H =50 oersteds. A material which ishighly satisfactory is barium ferrite, both oriented and non-oriented.Irregularly shaped particles of suitable size and configuration for useas magnet elements may be obtained by crushing a barium ferritepermanent magnet .and grinding the particles in a mill to the desiredsize. The mechanism for producing the alternating magnetic field may bea hollow solenoid of convenient shape and may be provided with amagnetic core to concentrate the magnetic field in the desired regions,as will be hereinafter set forth. The ampere turns or magnetic fieldintensity may be adjusted to best suit the conditions, the higher theliquid viscosity, the higher the desired magnetic field intensity. Thefrequency should be in a range to impart a suitable motion to the magnetelements, for example from about 1 to 100,000 cycles per second althoughcycles per second may be used to great advantage because of its readyavailability. Furthermore, while a sinusoidal alternating current may besuitably employed, a rectangular wave form alternating current may beused to advantage.

The alternating magnetic field imparts a random complex motion to themagnet elements. The magnetic moments impart rotation and spin to eachof the magnetic elements which tend to align themselves in properorientation with the magnetic field and the non-uniformity of themagnetic field imparts a translation motion thereto. The resultingmagnet element motion includes axial oscillations due to the inabilityof the magnetic elements to rotate a full 180 with each reversal of themagnetic field and thus results in a projectile type oscillatory motion.An additional spinning is due to the existence of torques, resultingfrom the lack of alignment of the alternating magnetic field and themagnetic axis of the magnet elements while in axial motion. Furthermore,the alternating magnetic field and the magnet field of the magnetelements promote the uniform dispersion or suspension of the magnetelements in the alternating magnetic field permeated fluid.

As aforesaid, the container or receptacle holding the fluid may be ofany desired shape and should be formed of a non-magnetic material suchas glass, synthetic organic plastics, for example, tefion, polyethylene,polypropylene and the like, ceramics, non-magnetic metals such ascertain of'the stainless steels, organic tissue, etc. Where the meansfor inducing the magnetic field includes a magnetic core it should be ofthe laminated or powdered type and preferably of a low Steinmetzcoefiicient to minimize eddy current and hysteresis losses. Followingthe stirring-0f the fluid; the magnet elements may easily be separatedtherefrom by halting'the alternating magnetic field and introducing aniron rod or permanent magnet into the fluid which will collect themagnetic elements which agglomerate on the iron rod.

Referring now to FIGURE 1 of the drawings, which illustrates a preferredembodiment of the present invention, the reference numeral 10 generallydesignates an annular shaped solenoid suitably mounted in a horizontalposition and connected by way of an adjustable autotransformer 11 orother current control means and a switch S to a source of alternatingcurrent. The parameters of the solenoid 10 and the alternating currentas well as the current in the solenoid 10 are as above set forth.Disposed on the solenoid 10 is a support plate 12 formed of anon-magnetic material and container'or receptacle 13 likewise of anon-magnetic material, for ex- V to establish an alternating magneticfield which permeates the liquid F and imparts a motion to each of themagnet elements 14 of the character set forth, the moving magnetelements, in turn, stirring and agitating the liquid F throughout thevolume thereof. It is important to note that in the absence of thealternating magnetic field the magnet elements will usually agglomerateor clump together into a ball or mass at the bottom of the vessel. Thisclumping or balling action is a result of the mutual attraction of thepermanent magnet particles which draws together as a coherent mass.However upon the establishment of the proper alternating magnet field,as aforesaid, the ball or mass literally explodes apart into thediscrete separated magnet elements which maintain their separateddiscrete identities as long as the alternating magnetic field ispresent. Upon discontinuance of the alternating magnetic field themagnet elements tend to clump and ball together thereby facilitatingtheir removal from the fluid. Thus the magnet elements are automaticallydistributed in the fluid by the motivating alternating magnetic field.

The intensity of the stirring and agitating action may be varied byadjusting the autotransformer 11 and hence the magnetic field intensity.It should be noted that the receptacle 13 may be of any configuration,may be open, or closed and sealed, may be heated and may be subjected toany ambient conditions, If it is desired to effect a stirring of greaterintensity in a selected region of the liquid F, a magnetic shim ormagnetic field forcussing or concentrating member, for example a softiron rod, or a permanent magnet, may be brought into the vicinity of theaforesaid region to thereby increaese the magnetic field intensity thereand the consequent stirring activity. Upon the completion of thestirring operation, the switch S is open, halting the motion of themagnet elements 14 and a soft iron rod or permanent magnet, is immersedin the liquid F to collect the magnet elements 14 which agglomeratethereon.

In accordance with a specific example of the present process employingthe above apparatus, it being understood that the example is givenmerely by way of illustration and is not intended to limit the scope ofthe present invention, the solenoid was of annular shape having a heightof 2 inches, an inner diameter of 1 /2 inches and an outer diameter of 3inches and contained 500 turns of wire. The solenoid was connected to asource of 60 cycles alternating current and the current therein wasabout 10 amperes. Where the liquid to be stirred was water or alcohol,100 magnet elements 14 were distributed in the liquid F, the magnetelements 14 being defined by irregularly shaped barium ferrite permanentmagnet elements having average diameters of 0.005 inch and where theliquid F was glycerine, the same number of magnet elements 14 wereemployed but their average diameter was about 0.100 inch. In each casethe stirring action was virtually instantaneous and at high amplitudes,easily produced frothing and an air-liquid suspension. In the aboveexample, the volume of the liquid F was about 50 milliliters in a 100milliliter beaker.

As seen in FIGURE 2 of the drawing, the receptacle for the liquid F maybe of various shapes, may be located in different positions relative tothe solenoid 10 and a plurality of receptacles may be subjected to thealternating magnetic field of a single solenoid. Specifically, thereceptacles include a closed container in the form of a stoppered bottle16 projecting through the opening in the solenoid 10, a shallow beaker17 located above the level of the solenoid 10 and a test tube 18registering with the solenoid opening. Each of the receptacles 16, 17and 18 contain a liquid F through which are dispersed magnet elements 14in number and size depending upon the viscosity of the liquid F and thevolume thereof and the desired intensity of stirring. In order toconcentrate or increase the stirring intensity in the region 19 of thereceptacle 16 a magnetic field directing and concentrating member 20 inthe form of a soft iron bar is supported in the vicinity of, and alignedwith the region 19 to increase the magnetic field intensity there, andconsequently the stirring activity. The field concentrating member 20may assume various shapes and sizes in accordance with the size andconfiguration of the region of increased stirring activity as may bedetermined by one skilled in the art.

In FIGURE 3 of the drawing, there is illustrated a form of apparatuswhich may be employed for effecting the stirring of selected layers orzones in a liquid. The

apparatus comprises a magnetic core or frame member 21 including abottom cross-piece 22, a pair of upright end legs provided with one ormore pairs of opposite legs 24 directed toward each other and havinglaterally spaced inner ends. Where more than one pair of legs 24 areprovided, as illustrated, the pairs are vertically spaced to permit thestirring of vertically separated layers of the liquid F. A solenoid 26is wound around the cross piece 22 and connected to a source ofalternating current as earlier set forth. A receptacle 27, for example,a beaker, contains a liquid consisting of three distinct layers orcomponents A, B, and C and registers with the magnet frame 21, the legs24 being aligned and colevel with the components A and C where stirringis desired independent of the intervening component B. Magnet elements14 are dispersed throughout the layers A and C and the stirring motionimparted thereto by the alternating magnetic field established betweenthe legs 24 of each pair and concentrated in the respective layers A andC. The intermediate layer B is substantially free of the magnet elements14 and is permeated by a relatively weak and substantially negligiblealternating mag netic field. It should be noted that where only onelayer section of a liquid is to be stirred only one pair of legs 24 isprovided. The legs 24 are preferably as wide as the transverse dimensionof the receptacle 27 so that the entire cross sectional area of thefluid at the desired levels is permeated by a strong alternatingmagnetic field. The magnet core 21 as well as the other magnet coresherein employed are constructed in the well known manner to minimizeeddy current and hysteresi losses and are preferably formed of highmagnetic permeable materials.

In FIGURE 4 of the drawing, there is illustrated another form ofapparatus which is suitable for the zone or layer stirring of a liquid.A test tube 28 containing a liquid F registers with the opening of anannular solenoid 10 connected to an alternating current source. A collar29 of soft iron or other magnetic material encircles the test tube 28 ata predetermined level and concentrates the alternating magnetic fieldproduced by the solenoid 10 at a corresponding level in the liquid F inthe test tube 28. Magnet elements 14 are suspended and motivated in theliquid F at the level of the collar 29 to stir the liquid in thecorresponding region. By varying the relative axial positions of thecollar 29 and the test tube 28 the stirring level may be accordinglyadjusted.

Another form of apparatus which is suitable for use with deep vessels isillustrated in FIGURE 5 of the drawing. The apparatus includes amagnetic core member base 32 comprising a cross member base 33 providedwith upright end legs 34 terminating in inwardly directed arms 36, and amedially located, upright bar 37 having a concavity formed in its upperface. A solenoid 38 is wound about the bar 37 and is connected to analternating current source to establish an alternating substantiallyvertical magnetic field extending from the level of the core arms 36 tothe bar 37. A vessel 35 in the form of a test tube extends verticallyfrom between the arms 36 to the bar 37 and contains a liquid having thepermanent magnet elements dispersed therethrough. Stirring of the liquidis effected by the magnet elements motivated by the aforesaidalternating magnetic field which permeates the liquid in the vessel 35.

Stirring and agitation of a continuously flowing liquid may be effectedby the apparatus illustrated in FIGURE 6 of the drawing. The apparatuscomprises a pipe or conduit 40 formed of a non-magnetic material and asolenoid 41 registering with a section of the conduit 40 and connectedto a source of alternating current. The stirring region 42 is delineatedby a pair of axially spaced perforated plates 43 extending across theconduit 40 at opposite sides of the solenoid 41. Aplurality of magnetelements are located in the region 42 and suspended in the liquidtherein and are larger than the openings in the plates 43 to preventtheir escape from the region 42.

The alternating magnetic field established by the solenoid 41 throughthe region 42 motivates the magnetic elements to stir andagitate theliquid therein. It should be noted that the conduit may be of anydesired configuration and follow any desired path and the region 43 mayextend for any desired length of the conduit and elongated solenoids ora plurality thereof may be employed. Furthermore, the cross section ofthe conduit 40 may vary along its length, as desired. Moreover, insteadof employing one or more solenoids 41 wound about the conduit 40 one ormore magnetic yokes may be substituted therefor of the type illustratedin FIGURE 3. Each yoke may be provided with only one pair of legs 24 andthe conduit 40 is located between and extends through the spacedelineated by the confronting yoke legs 24. The cooperating solenoids 26are connected to sources of alternating current, as aforesaid.

It should be noted that although the various embodiments of the presentinvention have been directed to the stirring and agitation of liquids,they are applicable to other fluid materials such as powders or thelike.

-While there have been described and illustrated preferred embodimentsof the present invention, it is apparent that numerous alterations,omissions and additions may be made without departing from the spiritthereof.

What is claimed is:

'1. The method comprising subjecting a plurality of separate, discrete,freely universally movable magnet elements having a coercive forceexceeding 50 oersteds to a magnetic field varying with time in directionand intensity to impart individual motions to said magnet elements.

2. The method of agitating a fluid comprising subjecting a plurality ofpermanent magnet elements having a coercive force exceeding 50 oerstedsdistributed in said fluid to a magnetic field periodically varying withtime in direction and intensity to impart motion to said permanentmagnet elements.

3. The method of agitating a liquid comprising dispersing a plurality ofpermanent magnet elements having a coercive force exceeding 50 oerstedsin said liquid and subjecting said permanent magnet elements to analternating magnetic field varying in intensity to impart rotationalmotions to the individual permanent magnet elements.

4. The method of agitating a liquid comprising dispersing a plurality ofpermanent magnet elements of nonspherical configuration and having acoercive force exceeding 50 oersteds in said liquid and subjecting saidpermanent magnet elements to a periodically alternating magnetic fieldperiodically reversing in direction and sinusoidally varying inintensity to maintain said permanent magnet elements in relative spacedrelationship and impart rotational motion thereto.

5. The method according to claim 4 wherein the maximum dimensions ofsaid permanent magnet elements are between 0.1 microns and 1 centimeter.

6. The method according to claim 5 wherein said permanent magnetelements each contain at least one magnetic domain.

7. The method according to claim 4 wherein said magnetic fieldalternates at a frequency between 1 and 100,000 cycles per second.

8. The method according to claim 4 wherein said magnetic field has astrength of at least 1 ampere-turn/ meter.

9. The method according to claim 4 wherein said magnetic field isconcentrated in a predetermined area of said liquid.

10. The method according to claim 4 wherein said fluid flowsthrough'said magnetic field while said permanent magnet elements remaintherein.

11. An apparatus comprising a container, a plurality of individualseparate magnet elements having a coercive force exceeding SOoerstedslocated in said container and means for establishing a magnetic fieldperiodically varying in intensity and direction through said containerin the region of said magnet elements.

12. An apparatus for stirring a fluid comprising a container for holdingsaid fluid, a plurality of non-spherical permanent magnetic elementshaving a coercive force exceeding 50 oersteds located in said fluid andmeans for establishing an intensity varying and direction alternatingmagnetic field through said fluid to maintain said permanent magnetelements in mutual spaced relationship and impart rotational motion tosaid permanent magnet elements.

13. An apparatus according to claim 12 wherein said container is formedof a non-magnetic material.

14. An apparatus according to claim 12 wherein said permanent magnetelements have a maximum dimension between 0.1 micron and 1 centimeter.

'15. An apparatus according to claim 12 wherein said permanent magnetelements are of irregular configuration.

16. An apparatus for stirring a fluid comprising a conduit through whichsaid fluid flows, a plurality of nonspherical permanent magnet elementslocated in said fluid, means for confining said magnet elements to apredetermined region in said conduit, and means for establishing anintensity varying and direction alternating magnetic field through saidfluid to maintain said permanent magnet elements in mutual relationshipand impart rotational and translatory motion to said permanent magnetelements.

17. An apparatus according to claim 12 wherein said means forestablishing said magnetic field includes a solenoid connected to asource of alternating current, said container being located in thevicinity of said solenoid.

18. An apparatus according to claim 12 including means for concentratingsaid alternating magnetic field in a predetermined region of said fluid.

19. An apparatus according to claim 18 wherein said concentration meansincludes a member of magnetic material disposed in the vicinity of saidpredetermined region.

20. An apparatus according to claim 18 wherein said concentrating meansincludes a collar of magnetic material encircling said container at apredetermined level.

21. An apparatus for stirring a fluid comprising a container for holdingsaid fluid, a plurality of non-spherical permanent magnet elementslocated in said fluid, and means for establishing an intensity varyingand direction alternating magnetic field through said fluid to maintainsaid permanent magnet elements in mutual spaced relationship and impartrotational and translatory motion to said permanent magnet elements,said means for establishing said magnetic field including a magneticcore member having a pair of arms disposed on opposite sides of saidcontainer and directed toward each other, and a solenoid coupled to saidcore member and connected to a source of alternating current.

22. An apparatus according to claim 21 including a plurality ofvertically spaced pairs of said core arms.

23. An apparatus for stirring a fluid comprising a container for holdingsaid fluid, a plurality of non-spherical permanent magnet elementslocated in said fluid, and means for establishing an intensity varyingand direction alternating magnetic field through said fluid to maintainsaid permanent magnet elements in mutual spaced relationship and impartrotational and translatory motion to said permanent magnet elements,said means for establishing said alternating magnetic field including amagnetic core member comprising a cross-piece provided with upwardlydirected end legs terminating in inwardly directed arms, said containerbeing disposed between said arms, a solenoid registering with saidcross-piece and means for connecting said solenoid to a source ofalternating current.

24. An apparatus for stirring a fluid comprising a container for holdingsaid fluid, a plurality of non-spherical permanent magnet elementslocated in said fluid, and means for establishing an intensity varyingand direction alternating magnetic field through said fluid to maintainsaid permanent magnet elements in mutual spaced relationship and impartrotational and translatory motion to said permanent magnet elements,said means for establishing said magnetic field including a magneticcore member comprising a cross-piece provided with upwardly directed endlegs terminating in inwardly directed arms and a medial leg projectingupwardly from said cross-piece intermediate the ends thereof, and asolenoid registering with said medial leg and connected to a source ofalternating current, said container being disposed between said inwardlydirected legs and in alignment with said medial leg.

1 0 References Cited by the Examiner UNITED STATES PATENTS CHARLES A.W-ILLMUTH, Primary Examiner.

LEO QUACKENBUSH, WALTER A. SCHEEL,

Examiners.

1. THE METHOD COMPRISING SUBJECTING A PLURALITY OF SEPARATE, DISCRETE,FREELY UNIVERSALLY MOVABLE MAGNET ELEMENTS HAVING A COERCIVE FORCEEXCEEDING 50 OERSTEDS TO A MAGNETIC FIELD VARYING WITH TIME IN DIRECTIONAND INTENSITY TO IMPART INDIVIDUAL MOTIONS TO SAID MAGNET ELEMENTS.